Hi Teasy, firstly, do not worry, you are doing the best you can by getting him seen asap and getting whatever it is diagnosed. Do not keep thought of the girl you know coming close to death as, like you said, no one knew she even had asthma.
My daughter was diagnosed with asthma when she was 3 years old after having a cough that wouldnt go. She had no other symptoms of a cold, no temperature, runny nose, aches and pains, just a cough. First they just kept giving anti biotics which helped, but the cough always came back when the course was finished. They then gave her ventolin medicine which really did do the trick. They went on to give her two inhalers and a chamber for her to take them through and she got better. I was told one of the inhalers, she was only to take when she seemed to need it ie. when she was weezing......... she never needed it. Then there were times when she would fall aslepp before I had had chance to give her her evening dose of the other inhaler...... it never affected her. I took her back and they decided she had never had asthma in the first place! Immediately I stopped with the inhalers and she has never been in need of anything like that since, she is now 6 years old.
Like many have mentioned, allergies are a major factor with asthma, and it turns out my daughter simply was having an allergic reaction to something. What, we never actually found out. The only thing she does need on occasions is something like piriteze medicine in the the summer as she does get hayfever, which incidently, causes the same symptoms as she had when she was three!
So try not too worry too much. he may not even have asthma but even if he has, it will easily be treated and controlled which will become apart of you and your sons everyday routine. You really have nothing to be afraid of.
Good luck this afternoon at the hospital :)